摘要:

Frechet differential corresponding to the inverse scattering of conductor cylinder is studied by adjoint operator theory. Numerical implementation of Newton-Kantorovich algorithm under successive plane wave illumination of different directions and frequencies is presented. Determination of initial values for iteration is introduced. Three kinds of bases for profile description of conductor cylinder are presented. Numerical results for each base are presented and compared with each other; thus, features of each base are revealed.

ISSN:0920-5071    

DOI:10.1163/156939397X00017

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A novel method for microwave imaging of lossless two-dimensional dielectric targets buried in layered media using time-domain scattering data with or without the effect of random noise is presented in this paper. It is an iterative method derived using volume equivalence principle, variation principle, Fourier transform. We name it as time-domain variational iterative method (TVIM). In each iteration, both the direct and inverse problems are solved once. The direct problem is solved by finite-difference time domain (FDTD) method and the inverse problem is solved iteratively. Numerical results show that TVIM performs much better than our former method. Those factors which make TVIM perform better are also investigated.

ISSN:0920-5071    

DOI:10.1163/156939397X00026

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The scattering of electromagnetic waves by periodic magnetodielectric structures with arbitrary profiles and inhomogeneous distribution of permittivity and permeability over a period is analyzed using rigorous integral equations of macroscopic electrodynamics and partitioning a structure into thin layers. The solution is found for E-polarized and H-polarized plane waves. Numerous examples of the problem solutions are compared with previously published results. Examples of approximation perfectly conducting periodic structures by magnetodielectric structures with the same geometry of a period are given. For illustration of the presented method effectiveness the analysis applies to a grating composed of circular magnetodielectric coaxial cylinders.

ISSN:0920-5071    

DOI:10.1163/156939397X00035

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper analyzes leaky modes in open microstrip lines. The different possibilities and implications of the choice of the inversion contour associated with the spectral domain analysis are investigated. Specifically, we have focused on the leaky solutions obtained when the inversion contour entirely lies either on the proper sheet or on the so-called outgoing sheet. Solutions computed on the proper sheet can be considered surface-wave leaky modes and those computed on the outgoing sheet volume-wave leaky modes. The continuity between the different bound and surface-wave/volume-wave leaky solutions has been studied. A new kind of spectral-gap effect has been found as a consequence of such study.

ISSN:0920-5071    

DOI:10.1163/156939397X00044

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper discusses the physics and aspects of the optimization of a type of near field radio frequency antenna which has been proposed for use in logging-while-drilling measurements. A numerical boundary element method is developed to provide accurate quantitative results. This two dimensional problem exhibits some features of the classical problem of minimizing losses in a long transmission line, except in a novel 'wrap around' geometry.

ISSN:0920-5071    

DOI:10.1163/156939397X00053

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A new explicit axisymmetric solver for the diffusion of electromagnetic fields in an inhomogeneous medium is described. The proposed method is based on the Krylov subspace (Lanczos) approximation of the solution in frequency domain. The finite-element method (FEM) is employed to discretize Maxwell's equations. It is shown that the spectral Lanczos decomposition method (SLDM) is extrernely fast. Furthermore, the electromagnetic fields at many frequencies can be evaluated by performing the SLDM iterations only at the lowest frequency. Analysis of some practical geophysical problems is included. A comparison is also made with the analytical results for a homogeneous medium.

ISSN:0920-5071    

DOI:10.1163/156939397X00062

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Biaxial -medium is an artifical material which is obtained by diffusion of planar conducting microstructures, having the shape of , into an isotropic dielectric medium with suitable orientations. In this paper, based on the eigen plane wave spectrum representation of the field and the Fourier expansion for the unknown angular spectrum amplitude, the cylindrical vcctor-wave-function representations of the electromagnetic fields in such materials are developed. It is shown that the solutions of the source-free Maxwell's equations for a biaxial -medium are composed of two cigenwaves traveling with different wave numbers, and each eigenwave is a superposition of two transverse waves and a longitudinal wave. The addition theorem of wave functions for biaxial media can be derived from that of wave functions for isotropic media. Applications of the theory are made to the case of two-dimensional scattering of a plane wave by a biaxial circular cylinder. Numerical results for some cases are presented.

ISSN:0920-5071    

DOI:10.1163/156939397X00071

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The Bargman transform is an outgrowth of the phase space representations of Electromagnetic Fields in Quantum Optics. It transforms fields from the time domain to the phase plane where they are functions of the phase variables p and q . The transform is another form of the windowed Fourier transform. The space in which the transform resides is called the Bargman space and has the important property that it contains analytic entire functions of the variable z = q ip. The analytic properties of the transform are utilized to construct phase space filters which are used to selectively access portions of the phase plane. The phase space filtering is used to analyze target returns from canonical targets such as dielectric slabs and perfectly conducting spheres.

ISSN:0920-5071    

DOI:10.1163/156939397X00080

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A hybrid numerical boundary condition (HNBC) with the same accuracy as surface integral methods, applicable to an absorbing boundary with an arbitrary shape, is proposed. The HNBC is a global boundary condition resulting in a dense submatrix due to the coupling of all boundary nodes. In many cases, the HNBC can be approximated by another set of boundary conditions where only a few boundary nodes are coupled together to preserve the sparsity of the resulting matrix equation. One special approximation will result in the measured equation of invariance (MEI) method. Another approximation will result in a nonlocal numerical boundary condition (NNBC), of which the MEI method is a subset. For the NNBC, the sparsity of the resulting finite element matrix is preserved, although the boundary condition is nonlocal. Numerical results for a class of 2-D problems are presented to illustrate the accuracy of the original global hybrid numerical boundary condition and the nonlocal numerical boundary condition.

ISSN:0920-5071    

DOI:10.1163/156939397X00099

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939397X00107

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor